Modifications in cytoskeletal proteins are an important concomitant of age-related diseases of the brain (e.g. Alzheimer's disease). However, there is little information about the age- related changes of cytoskeletal components in normal neural cells. In this proposal we will use the neuromuscular system as a model to study the effects of aging on cytoskeletal elements. The neuromuscular system has several advantages of such studies including: 1) its accessability for sampling and manipulation and 2) previous demonstrations (from our and other laboratories) of age-related changes in its structure, function and ability to grow. The overall goal of the proposed experiments is to evaluate age- related changes in neurofilament and tubulin proteins in normal and growing axons. The relation between cytoskeletal changes and the loss of synaptic plasticity with aging will be evaluated in mammalian peripheral nerve and neuromuscular junction. Methodology will include morphometric analysis of peripheral nerves and neuromuscular junctions, gel and immmunoblot analysis of axonal proteins, immunohistochemical staining of axonal elements, ELISA measurement of cytoskeletal elements, and electron microscopy. The results of these studies will provide new information about the changes in specific cytoskeletal elements that occur during aging. This data will shed light on the biology of the cytoskeleton in aging neurons and axons, including changes in synthetic processes and post translational mechanisms. We and others have previously found that there is a loss of neural structure, function and plasticity with aging. Our results should provide information about the cytoskeletal changes associated with this loss of function. The techniques used will be applicable to similar processes occurring in normal humans and in age- related disorders such as motor neuron diseases.